Consequences of bulk odd-frequency superconducting states for the classification of Cooper pairs

TL;DR

This paper investigates the symmetries and magnetic properties of subdominant Cooper pair correlations in inhomogeneous superconductors, revealing a classification into eight classes based on their symmetry and magnetic response.

Contribution

It provides a comprehensive classification of Cooper pairs considering their frequency symmetry, parity, and magnetic response, including in odd-frequency superconductors.

Findings

Subdominant pairing correlations have opposite symmetry and magnetic properties to the dominant ones.

Cooper pairs can be classified into eight distinct classes based on their symmetries and magnetic responses.

Anomalous magnetic properties can be detected via the Meissner effect.

Abstract

We analyze symmetries and magnetic properties of Cooper pairs appearing as subdominant pairing correlations in inhomogeneous superconductors, on the basis of the quasiclassical Green-function theory. The frequency symmetry, parity, and the type of magnetic response of such subdominant correlations are opposite to those of the dominant pairing correlations in the bulk state. Our conclusion is valid even when we generalize the theory of superconductivity to recently proposed diamagnetic odd-frequency superconductors. As a consequence, Cooper pairs are classified into eight classes in terms of their symmetries and magnetic properties. Anomalous magnetic properties of subdominant components can be probed by studying the Meissner effect.